Printed security device and method

ABSTRACT

According to one aspect of the invention, a printed security device for a document comprises an intaglio printed latent image which has been printed onto a substrate using a highly reflective ink, wherein the intaglio printed latent image is visible when viewed within a first angle range extending from near-vertical to the plane of the latent image towards the image and also within a second angle range closer to the plane of the image, and is not visible when viewed within an angle range between the first and second angle ranges. A change in viewing angle from one angle range to an adjacent angle range results in a visible latent image becoming invisible or vice versa (creating a flip-flop image visibility effect). According to another aspect of the invention a non-intaglio printed second image is added, preferably between the substrate and the intaglio printed latent image, wherein the second image is visible when viewed within an angle range between the first and second angle ranges of visibility of the intaglio printed latent image and is not visible when viewed at other angles. The flip-flop image visibility effect is thereby enhanced such that distinct images (viz. the intaglio latent image and non-intaglio image) are viewed as the viewing angle of the security device moves from near-vertical to near-horizontal angles.

FIELD OF THE INVENTION

This invention relates generally to the field of printed matter for useon documents such as documents of value (e.g. banknotes), passports,identity documents, and the like and, more particularly, to printedmatter in the form of a security device, and method of making the same,configured for facilitating an authentication of the document by meansof a simple, visual inspection.

BACKGROUND OF THE INVENTION

Intaglio printing is typically used for the manufacture of documents ofvalue such as bank notes for which counterfeiting and fraudulent actionsare a cause of concern. According to this printing method, a substratesuch as a high grade paper is pressed against an engraved and inkedplate, at very high pressure, so as to cause the substrate to deforminto ink-bearing engraved recesses of the plate and thereby produce aninked impression on the substrate, the appearance of which is defined bythe engravings and is difficult to replicate without using an intaglioprinting press.

However, with the advent of improved technologies for photocopiers anincreased risk of counterfeiting of intaglio-printed documents, usingphotographic techniques, has developed. These new technologies can becapable of reproducing intaglio-printed documents with sufficientquality to be able to avoiding detection by lay persons relying only ona visual inspection of the reproduced document. Consequently, there is aneed for means to enable authentication of such documents through asimple visual inspection of the document (i.e. without the use ofspecial knowledge or experience, finding screens, special lights orsimilar tools).

Certain specific printed security devices are known for facilitatingsuch authentication but, by reason of their manner of use and limitedvisual effects, these known devices are primarily directed to trained orknowledgeable security personnel rather than for the use of lay persons.For example, U.S. Pat. No. 4,033,059 to Hutton et al describes anintaglio printing of two images, one being a background image and theother a latent image, using differing orientation or depths for theintaglio imprints such that the latent and background images are notdiscernible and appear as a single image when viewed from a normalviewing angle roughly perpendicular to the document but when viewed fromthe side (i.e. at a narrow angle to the plane of the document) thelatent image stands out as an independent image separate and discerniblefrom the background. According to that security device it is necessaryto decrease the viewing angle (that is the angle to the plane of thedocument) in order to establish and then improve the visibility of thelatent image. Similarly, U.S. Pat. No. 5,199,744 to Shenton describes asecurity device comprising a substrate which is embossed with atransitory image on one area of a substrate, the transitory image beingvisible at a specific angle only and not at other angles, and a lineararea around the image which is visible at all angles, such that when thedevice is viewed at angles other than the specific viewing angle auniform image is seen and the transitory image (being either a latent ortransient image) is not discernible (this being discernible as aseparate image only when viewed at the specific viewing angle). Thus,for both of these known security devices their effective use is directedto persons having knowledge of the applicable viewing angles.

Another example is a security device described in Canadian Patent No.1,172,282 to Merry whereby a first line deflection pattern, defining afirst image which is detectable by using a finding screen there over,overlays a second line deflection pattern, defining a second image whichis detectable by using a finding screen there over, the two patternsbeing printed at different angles of orientation such that each image isseparately detectable using a finding screen oriented at such differentangles. Similarly, Canadian Patent No. 2,071,795 to Merry et aldescribes a security device comprising an array of micro-characters inwhich a group of the characters is phase-shifted relative to the othersto collectively define an image, whereby the characters appear uniformwhen viewed by the naked eye and the image is not disvernible but withthe aid of a finding screen the image becomes visible. Effective use ofthese security devices by persons requires such persons to beknowledgeable with respect to the such use and also requires a specificfinding screen.

There is a need, therefore, for a security device which is useablewithout prior knowledge by the user. Further, there is a need for asecurity device which can be applied to a document using conventionalprinting and is relatively simple and avoids high manufacturing costs.Still further, there is a need for a security device which provides adistinct visual effect as compared with those created by the knownlatent and transient images described in the foregoing patentreferences.

SUMMARY OF THE INVENTION

In accordance with aspects of the invention there are provided a printedsecurity device for a document and a method of making the same. Anintaglio printed latent image is printed onto a substrate using a highlyreflective ink, such that the intaglio printed latent image is visiblewhen viewed within a first angle range extending from near-vertical tothe plane of the latent image towards the image and also within a secondangle range closer to the plane of the image, and is not visible whenviewed within an angle range between the first and second angle ranges.In the result, a change in viewing angle from one angle range to anadjacent angle range results in a visible latent image becominginvisible or vice versa (producing a flip-flop image visibility effect).

In accordance with a further aspect of the invention a second image isprinted by non-intaglio printing, such that the second image is visiblewhen viewed within a third angle range between the first and secondangle ranges (for example, in the illustrated embodiment the third anglerange commences at about 12°-17° from the vertical to the plane of theimage) and is not visible when viewed at other angles. In the result, achange in viewing angle between the first angle range and the thirdangle range results in a visible latent image becoming invisible and aninvisible non-intaglio printed second image to become visible, or viceversa. Also, a change in viewing angle between the third angle range andthe second angle range results in a visible non-intaglio printed secondimage becoming invisible and an invisible latent image to becomevisible, or vice versa (thereby also producing a flip-flop imagevisibility effect but with the improvement of the visible imagesalternating between the distinct latent and second images).

Preferably the highly reflective ink is a bright metallic inkcomprising, by weight percentage, 30%-60% varnish, 0-15% solvent, 0-5%wax, 24%-60% metallic pigment and 0-5% drier. The second image isprinted using an iridescent ink which may, for example, comprise, byweight percentage, about 65% clear varnish, about 23% thinner and about12% iridescent pigment. Preferably the second image is printed by screenprinting over the substrate and the intaglio printed latent image isprinted over the second image.

DESCRIPTION OF THE DRAWINGS

The present invention is described below with reference to the followingdrawings in which like reference numerals refer throughout to likeelements.

FIG. 1 is an exemplary depiction of a bank note on which there has beenprinted a security device in accordance with the invention, whereby theappearance of the security device when viewed at a near-vertical angleto the plane of the image is shown, such that an intaglio printed latentimage (viz. the word “OKAY” in this example) associated with thatnear-vertical angle is visible;

FIG. 2 is a further depiction of the bank note of FIG. 1, with securitydevice, but as seen at a different viewing angle (e.g. 17° in thisexemplary embodiment) which is within an angle range adjacent to a firstangle range of visibility for the latent image of FIG. 1, whereby anon-intaglio printed second image (viz. the letter “A” with a circledesign” in this example) associated with this different viewing angle isvisible instead of the latent image shown in FIG. 1; and,

FIG. 3 is an exaggerated cross-sectional view of the security deviceshown in FIG. 1 (or FIG. 2) taken at section I—I, illustrating thesubstrate and print layers of the security device of the document shownby FIGS. 1 and 2.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

Prior to the present invention it had been believed by persons skilledin the art of intaglio printing that intaglio printed latent images aresubject to becoming visible at low angles (acute to the plane of theimage) only and that they are not subject to becoming visible at anglesclose to the vertical (perpendicular to the plane of the image), thereason being that this was the effect which resulted from the differingorientation or depths for the intaglio imprints defining the latentimage (for a basic description of the making of an intaglio printedlatent image reference may be made, for example, to U.S. Pat. No.4,033,059 to Hutton et al). For example, this effect is taught in U.S.Pat. No. 5,199,744 to Shenton at column 6, lines 19-21, wherein it istaught to use a perimeter line around an intaglio printed latent imagein order to be able to identify the area of the latent image from above,it being alleged therein that latent images are designed only to berevealed a low angle viewing.

The inventors have made the unexpected and surprising finding that byusing a highly reflective intaglio ink (alternatively referred to hereinas a bright metallic intaglio ink) to intaglio print a latent image, thevisibility of the latent image is caused to change markedly over thatwhich applies when a non-reflective (regular) intaglio ink is used.Specifically, when a highly reflective intaglio ink is used the latentimage is visible at a viewing angle close to 90 degrees (i.e. close tothe vertical from the image plane) in addition to being visible at theprior low viewing angle (i.e. an acute angle to the image plane). In thecontext of the foregoing prior art latent images, this close to verticalvisibility of the latent image would be undesirable since the intentionthere is that the latent image be secret and known only by thoseknowledgeable person assigned to search for them for purposes ofauthenticating a document. However, the inventors recognize that thisdual high-low angle imaging is, in and of itself, a useful advancementfor securing and authenticating a document because such an ability tosee the image on a printed security device, upon a normal (i.e. close tovertical) viewing of the document, enables lay persons to assess theauthenticity of the security device. At the same time, a simple handlingof the security device, moving it slowly in different directions tocontinuously change the viewing angle from high to low, results in arepetitive appearance and disappearance of the latent image, since itbecomes visible at high and low angles and invisible at angles betweenthem, thereby establishing a hologram or “flip-flop”-type visual effectfor the security device.

The specific angles of visibility of an intaglio latent image printedwith a highly reflective intaglio ink will vary from one intaglio printsituation to another because the viewing angles associated with anygiven latent image are dependent upon design variations and theorientation, widths and heights of the engraved lines. Also, theintensity and direction of the light source for a given viewingsituation will affect the visibility of the latent image the angle atwhich the light falls on the document (for example, whether the vieweris facing a window or, instead, is sideways to it, will result in theflip-flop effect occurring at different angles). However, in general,for an intaglio latent image printed with a highly reflective intaglioink, it is found by the inventors that the intaglio printed latent imageis visible when viewed within a first angle range extending fromnear-vertical to the plane of the latent image (i.e. approximately 90°to the plane of the image) towards the image and also within a secondangle range separate from the first angle range and extending fromcloser to the plane of the image (i.e. approximately 10° to the plane ofthe image) towards the plane of the image (i.e. the horizontal). Thelatent image is not visible when viewed within an angle range betweenthese first and second angle ranges. Thus, a change in viewing anglefrom one angle range to an adjacent angle range (i.e. moving from anangle within the first angle range to an angle within the angle rangebetween the first and second angle ranges or vice versa, or from anangle within the angle range between the first and second ranges to anangle within the second angle range or vice versa) results in a visiblelatent image becoming invisible or an invisible latent image becomingvisible. It is the foregoing first angle range, starting about thevertical to the image, which is new and which does not occur forintaglio latent images printed with regular (i.e. not highly reflective)inks.

In addition, the inventors have developed an even further improvedsecurity device 10 comprising two separately printed and distinct images80, 90, whereby each becomes visible when viewed at a different angle,or range of angles, than the other, the resulting visual effect being adistinct flip-flopping between the two images as the document 20 ishandled. Examples of these two images 80, 90, one being an intaglioprinted latent image 80 and the other being a non-intaglio printed image90, are depicted by FIGS. 1 and 2. Advantageously, the use of intaglioprinting enhances the degree of security of the document becauseintaglio printing is inherently more secure than other types of printingdue to the specialized, expensive printing equipment needed to performintaglio printing.

The intaglio printed latent image 80 is printed using a highlyreflective ink and provides a high angle visibility (in fact, a dualhigh-low visibility). A second printed image 90, using a non-intaglioform of printing and an iridescent ink, provides a mid-angle visibilitywhereby the second image is visible when viewed at an angle within athird angle range between the first and second angle ranges ofvisibility of the latent image 80. Thus, the latent image 80 is visibleat near-vertical angles to the plane of the security device. Then, whenthe viewing angle is moved away from those near-vertical angles andbecomes within the third angle range of visibility of the second image(this angle being closer to the horizontal of the plane of the securitydevice but not so close as to reach the low viewing angle range of thelatent image 80), the non-intaglio printed second image 90 becomesvisible. Again, it is to be understood that it is not possible toprecisely specify the viewing angle ranges for the images 80, 90, sincethis depends on many variable factors including the intensity anddirection of the light source. For the illustrated embodiment (accordingto which the non-intaglio image 90 is printed first, before the intaglioprinting is applied, using a particular selected iridescent ink andsilkscreen printing) the non-intaglio image 90 becomes visible at about12°-17° from the vertical to the plane of the image and remains visiblewithin a third angle range which is between the first and second angleranges of visibility of the intaglio image. Thus, a change in viewingangle from one angle range to an adjacent angle range (i.e. from thefirst to third angle range or vice versa, or from the third to secondangle range or vice versa) results in a visible latent image becominginvisible and an invisible second image becoming visible, or vice versa.

For the illustrated embodiment of the security device 10, the images 80,90 occupy print layers 50, 40, respectively, over a substrate 30 whichis of a sufficiently high quality to receive intaglio printing e.g. banknote paper (see FIG. 3). In this example, the non-intaglio printed image90 is printed firstly, to form a first print layer 40 over the substrate30, using a screen press. Advantageously, screen printing is capable oflaying down a heavy ink film, as compared with other non-intaglioprinting methods such as lithography, gravure, flexography andletterpress, and this is pertinent because the visibility of iridescentink images, such as image 90, is dependent on the thickness of the inkfilm deposited. By appropriate selection of the ink used for thisprinting, and configuration of the printed image, the non-intaglioprinted second image 90 becomes visible only within a predeterminedangle range at which the latent image is no longer visible i.e. theimage 90 becomes invisible at angles outside the predetermined anglerange of visibility therefore (referred to herein as the third anglerange).

To achieve this complementary visibility of the non-intaglio image 90, asuitable iridescent ink (i.e. an ink having iridescent pigments) isselected for use, such inks being well known in the printing industryand a person skilled in this industry being readily able to make asuitable selection. For the illustrated embodiment the ink formation setout below under Table A, is used for silkscreen printing of thenon-intaglio image 90. It is to be understood that although thenon-intaglio image 90 is preferably printed first according to theillustrated embodiment, and the intaglio latent image is printedthereafter, it also possible to print the latent image first and thenprint the second non-intaglio image over it. Also, it is to beunderstood that although the preferred printing method is to use ascreen press for the non-intaglio image 90, it is possible to use otherprinting methods such as lithography, flexography or gravure printing.

TABLE A Ink Formulation for Sample Silkscreen Printed Image ComponentAmount (by weight percentage) MPI 170¹ clear varnish 65 MPI 182G¹thinner 23 Afflair 205² pigment 12 Total: 100 Notes: ¹Productidentifier, available from Tecknecal Screen Print Supplies Inc. ofClarence Creek, Ontario, Canada. ²Product identifier, available from EMIndustries of Hawthorne, New York, U.S.A.If desired, this ink may be formulated to have other special properties,in addition to being visible only within a predetermined angle range,such as being fluorescent, phosphorescent or thermochromic.

For the illustrated embodiment, the intaglio printing of the latentimage 80 is performed secondly using a highly reflective ink so that theimage 80 is visible at a close to vertical angle from the plane of theimage. The intaglio imprints 60 define a second print layer 50 over thefirst print layer 40. The highly reflective ink used for the illustratedembodiment is the bright metallic intaglio ink developed by the assigneeof the present invention as described in U.S. Pat. No. 6,063,176. Otherbright metallic inks suitable for use are well known by persons skilledin the art and are readily available in the marketplace. These inks usemetallic pigments, iridescent pigments, special effect pigments such asthe Paliocrom* (*trademark) pigments available from BASF of Germany. Theintaglio OVI* (*trademark) ink manufactured by Sicpa of Switzerland isalso suitable for use. For the illustrated embodiment the ink formationset out below under Table B, is used for intaglio printing of the latentimage 80.

TABLE B Ink Formulation for Sample Intaglio Printed Image Amount (byweight percentage) Component [and optional percentage range] Varnish  35[30-60] Solvent  6 [0-15] Wax  3 [0-5] Metallic pigment  55 [25-60]Driers  1 [0-5] Total: 100

Persons skilled in the field of security printing will be readily ableto apply the present invention to implement various applications of thesame. Consequently, it is to be understood that the particularembodiment described herein by way of illustration is not intended tolimit the scope of the invention claimed herein by the inventors anddefined by the appended claims.

1. A printed security device for a document, said security devicecomprising an intaglio printed latent image which has been printed ontoa substrate using a highly reflective ink, wherein said intaglio printedlatent image is visible when viewed within a first angle range extendingfrom near-vertical to the plane of said latent image towards said imageand also within a second angle range closer to the plane of the image,and is not visible when viewed within an angle range between said firstand second angle ranges, whereby a change in viewing angle from one saidangle range to an adjacent angle range results in a visible said latentimage becoming invisible or an invisible said latent image becomingvisible.
 2. A printed security device according to claim 1 and furthercomprising a non-intaglio printed second image, wherein said secondimage is visible when viewed within a third angle range between saidfirst and second angle ranges and is not visible when viewed at otherangles, whereby a change in viewing angle between said first angle rangeand said third angle range results in a visible said latent imagebecoming invisible and an invisible said non-intaglio printed secondimage becoming visible or vice versa.
 3. A printed security deviceaccording to claim 2 whereby a change in viewing angle between saidthird angle range and said second angle range results in a visible saidnon-intaglio printed second image becoming invisible and an invisiblesaid latent image becoming visible or vice versa.
 4. A printed securitydevice according to claim 1 wherein said highly reflective ink is abright metallic ink comprising, by weight percentage, 30%-60% varnish,0-15% solvent, 0-5% wax, 24%-60% metallic pigment and 0-5% drier.
 5. Aprinted security device according to claim 3 wherein said second imageis printed using an iridescent ink.
 6. A printed security deviceaccording to claim 5 wherein said highly reflective ink is a brightmetallic ink comprising, by weight percentage, 30%-60% varnish, 0-15%solvent, 0-5% wax, 24%-60% metallic pigment and 0-5% drier.
 7. A printedsecurity device according to claim 6 wherein said iridescent inkcomprises, by weight percentage, about 65% clear varnish, about 23%thinner and about 12% iridescent pigment.
 8. A printed security deviceaccording to claim 7 wherein a print layer defined by said non-intaglioprinted image is between said substrate and a print layer defined bysaid intaglio printed latent image.
 9. A printed security deviceaccording to claim 8 wherein said non-intaglio printed image becomesvisible at about 12°-17° from the vertical to the plane of the image.10. A method of making a printed security device for a document, saidmethod comprising intaglio printing a latent image onto a substrateusing a highly reflective ink, whereby said intaglio printed latentimage is visible when viewed within a first angle range extending fromnear-vertical to the plane of said latent image towards said image andalso within a second angle range closer to the plane of the image, andis not visible when viewed within an angle range between said first andsecond angle ranges, such that a change in viewing angle from one saidangle range to an adjacent angle range results in a visible said latentimage becoming invisible or an invisible latent image becoming visible.11. A method according to claim 10 and further comprising non-intaglioprinting a second image, whereby said second image is visible whenviewed within a third angle range between said first and second angleranges and is not visible when viewed at other angles, such that achange in viewing angle between said first angle range and said thirdangle range results in a visible said latent image becoming invisibleand an invisible said second image becoming visible or vice versa.
 12. Amethod according to 11 whereby a change in viewing angle between saidthird angle range and said second angle range results in a visible saidsecond image becoming invisible and an invisible said latent imagebecoming visible or vice versa.
 13. A method according to claim 10whereby said highly reflective ink is a bright metallic ink comprising,by weight percentage, 30%-60% varnish, 0-15% solvent, 0-5% wax, 24%-60%metallic pigment and 0-5% drier.
 14. A method according to claim 12whereby said second image is printed using an iridescent ink.
 15. Amethod according to claim 14 whereby said highly reflective ink is abright metallic ink comprising, by weight percentage, 30%-60% varnish,0-15% solvent, 0-5% wax, 24%-60% metallic pigment and 0-5% drier.
 16. Amethod according to claim 15 whereby said second image is printed byscreen printing.
 17. A method according to claim 16 whereby saidiridescent ink comprises, by weight percentage, about 65% clear varnish,about 23% thinner and about 12% iridescent pigment.
 18. A methodaccording to claim 17 whereby said second image is printed over saidsubstrate and said intaglio printed latent image is printed over saidsecond image.
 19. A method according to claim 18 whereby said secondimage becomes visible at about 12°-17° from the vertical to the plane ofthe image.